Htobation of ousfineb



Reiuued Jan. 9, 1940 PATENT orr'lca warrior: or omrmns Alfred W. Francis, Woodbury, N. 1., auignor to Socony-Vacuum Oil Company, Incorporated,

a corporation of New York No Drawing. Original No. 2,055,720, dated September 29, 1936, Serial No.

693,151, October f 11, 1933. Application for reissue December 29,

1937, Serial No. 182,386

Claims. (01. zoo-e14) This invention relates to the manufacture of isopropanol and diisopropyl ether from propylene.

The purpose of the invention is the economic conversion of propylene, through direct hydration, into isopropanol and diisopropyl ether by a simple process in which no material other than propylene and water is consumed.

If propylene be treated either alone, or bination with inert gases such as propane, by

contact, under elevated temperature and pres-' sure, with sulphuric acid of about 20% to 65% concentration, the propylene may be converted directly and rapidly into isopropanol and diisopropyl ether, and the relative quantities of these products may be controlled by the molalratio between the propylene and the water present.

The efiiciency of the process is'a function of acid concentration and temperature, but these quantities, at their permissible maxima, vary in-' versely, the limits being those which cannot be exceeded without undesirable side reactions. Owing to this inverse variation, the process may be carried out emciently with acid varying in concentration through a range from about 20% to 65% at the appropriate corresponding temperatures, provided a pressure be used such asto give a sumcient density'to the propylene at the reaction temperature.

centrations call for higher temperatures and Since the lower acid conpressures to secure emcient results, I prefer to work nearer the upper limit'of concentration. With acid of 60% concentration 100 degrees C. is a suitable temperature, which can be conveniently maintained by the use of steam, and a corresponding initial pressure of about 600 lbs. or more is sufllcient,

Since the reagents and the products of the process are present in a vapor phase and one or two liquid phases, it is necessary, for practical efficiency, to agitate the contents of the reaction vessel constantly in such a manner as to maintain an intimate dispersion or foam in which i there is extended contact between the vaporous and the liquid constituents.

The isopropanoi which is the immediate result of the hydration is a solvent of propylene, so that as it accumulates it increasingly assists in maintaining adequate concentration of the propylene and intimate contact with the acid catalyst. For this reason, the pressure necessary for eflicient operationis only initially dependent uponthe vapor density of the propylene. When the process is conducted hermetically in an autoclave, the consumption of a part of the propylene. and thesolution of a part of the remainder in in com-- .the cracking of petroleum, it is the isopropanol, result in a substantial fall of pressure, but if the reagents, when introduced in the proper molal ratio and quantity, produce an initial pressure nearly equal to the vapor pressure of propylene at the reaction temperature, or to its extrapolated pressure in case the'reactio'n temperature is above the critical temperature, the

reaction may be carried out nearly to equilibrium with a continuing high efiiciency. When the production of the desired "end products has reached about 90% of the theoretical quantity for equilibrium, however, the rate of production falls off so rapidly that it is economical to interrupt the operation at'that point.

Where the process is carried out in a continuous manner, the pressure may be maintained constant with some increase in efllciency.

The result of the reaction, when carried to or near to equilibrium, is always the production of both isopropanol and diisopropyl ether, but the ratio in which theyl occur may be controlled by using propylene and water in different molal ratios. When the alcohol is desired the ratio of propylene to water should be not over 1:1, the preferred ratio being 0.8:1. When the ether is desired the ratio may be between 2:1 and 5: 1', the preferred ratio being 2.5: 1. If intermediate molal ratios are used considerable quantities or both alcohol and ether will result.

It is not necessary that the propylene be pure, but it is desirable that it be separated from other olefineswhich may be polymerized or hydrated under the conditions of the reaction. Where the propylene is derived from the gases produced in feasible, by fractional distillation, to separate the propylene in a fraction which contains, in addition, only saturated hydrocarbons which do not interfere with the process. In the process as hereinafter speciflcally described the raw material is a mixture of propylene and propane such as may be secured by such fractionatiom'the propane being inert under the operating conditions.

In working for alcohol, after the interruption of the reaction the alcohol is preferably distilled off from the dilute acid as a constant-boiling mixture of alcohol and water. Since this results in concentration of the acid, it is necessary to add, before or during the distillation, enough water to prevent concentration of the acid beyond about Preferably, the distillation is preceded by the addition of an amount of water equal to the sum oi. that consumed in the reaction and that removed with the alcohol, so that upon completionofthedistiliationtheacidhasitsoriginal is nearly the same as that that the two liquids may easily be maintained in a concentration and is ready for use again in the same process. The acid sufiers no substantial loss or contamination, so that it may be re-used indefinitely.

when working for ether. the liquids separate into two layers, the upper layer containing substantially all the ether and the lower layer containing the dilute acid and such alcohol as has been produced. In this case it is desirable to leave the alcohol in the acid solution and merely dilute with the necessary water to restore the 7 acid to be proper concentration for use, since the alcohol so retained acts usefully as a solvent for the propylene and also promotes the attainment of the equilibrium from which the ether results.

In working for alcohol also it is feasible to leave some alcohol in the acid solution when prepared for re-llse, and suchalc hol, serving from the outset as a solvent for the propylene, reduces themaximum or initial pressure necessary for a given rate of reaction. On the other hand, however, the alcohol so retained constitutes partof the'equilibrium proportion. and thus reduces the" may be produced at quantity 'of alcohol which each operation.

The useful solvent function performed by the isopropanol may be supplemented by the use of some auxiliary solvent. Such auxiliary solvent has the advantage that it reduces the pressure. or the degreeof agitation. n to secure a given rate of reaction. while it does not affect the equilibrium of the reagents and products, if it be a material which is inert under the conditions of the reaction. various inert solvents which are immiscible with the dilute acid may be used. including hydrocarbons and halogenat ed hydrocarbons. chloroform, when used as a solvent, has the advantage that. when containing the dissolved propylene, its specific gravity of the dilute acid, so

an emulsionz' 7 Water-soluble solvents, such as aliphatic alcohols. may also be used, but as these react to somtiigxtent, the products of the reaction will con diisopropyl ether.

While the stated limits of 20% may. acid concentration are not absolute, I have found that the'emciency of the process falls ofl rap-- idly as the concentration is reduced below about 20%. when a concentration greater than about 60% is used it is necessary, after distilling oi! the alcohol, to reconcentrate the acid before itcanbeused again.

.No absolute relation between acid strength and temperature can be fixed, since increase in temperature for a given strength results both in accelerated rate of reaction and in increased tendency to undesirable reactions. so that the advantage and the disadvantage must be weighed against each other economically. The

temperatures corresponding tovarious acid concentrations which I have found most desirable.

however. are approximately as in the following table: I

rmtmso. y,

as m um IL 140 1.12s 4a an 1,110 at m 1,000 on me gm compounds other than isopropanol. and

- formed in addition.

It is inadvisable to-exceed these temperatures by more than about30 degrees.

It will thusbe seen from the foregoing that the relationship between the acid concentration and the temperature at which the hydration of propylene is carried out in accordance with my invention is such that at the respective acid concentrations of about about about 40%, about and about the temperature range corresponding to each of these acid concentrations is respectively between about C. and about 180' 0.; between about 140 C. and about 0.: between about 130 C. and about (2.; between about 120 0.; and 150C.: and between about 100' C. and about 130 (3;, it being imderstood also, ofcourse. that the different temperature ranges (extending over about 30 0.) corresponding to the diiferent acid concentrations intermediate between the specific concentrations shown in the above table may be readily estimated by interpolation (as by graphic interpolation, by plotting suitable curves on rectangular coordinates as will be readily understood by those skilled in the art).

In the same table pressures are shown which give the undissolved propylene, at the corre sponding temperature. a density of about 0.23.

which is approximately its density at the critical temperature. These pressures may be deemed those for optimum results. since the rate of reaction falls ofi substantially as they are reduced, while little is gained by exceeding them. For practical commercial results it is probably necessary to use at least 80% of the given pressure in each case.

It should be understood that the given li sures have reference particularly to the use of' pressure at which economically practical results can be secured at any given temperature and acid concentration.-

The following example illustrates application of the process'when working particularly for the production of isopropanol. A mixture consisting of 49.3 g. of propylene and 22.7 g. of

propane was placed in an autoclave of 360 ml.

capacity, 'together with 78 g. of aqueous sulphuric acid containing 60% acid .by weight.

The temperature was maintained at 100 degrees- 0., and the initial pressure. was 680 lbs. gage.

The contents of the autoclave were'maintained, by strong agitation, in a thoro shiy mixed condition for three hours, during which time the pressure fell to 4'75 lbs. The contents ofthe autoclave were then cooled and separated. 12.2 g. of propylene remained uneombined. The liquid products were diluted with 18 g. of water and distilled throuflh a. column, giving 45 g. of a distillate boiling at 80 degrees C. and containing 81% or- 39 g. of isopropanol, showing a conversion. to isopropanol of 57% of the Propylene charged. ut 1 g. of diisopropyl ether was The following example illustrates the process as operated with a view to the production of ether. of propane was placed in thesame autoclave as before. together with 32 g. of aqueous sulphuric acid, of 00% concentration by weight, and the contentsoftbeautoclaveweremaintaineqat lid A mixture of 01 g. of propylene and 38 g. 1

the operation, 16.2 g. of propylene remained. 13

g. of water was added to the liquid products which separated into two layers. layer contained 38.2 g. of diisopropyl ether and 1.2 g. of water and isopropanol. The lower layer comprised. acids of proper concentration for re-use in thesameprocess. Upon analysis it was found to contain 13.5.g. of lsopropanol 4 which could either be left with the acid for resential feature of the process.

use, or removed as a lay-product. Of the propylene charged to the autoclave, 52% was converted to diisopropyl ether and 16% to isopro-,

panol. a

The acid concentration of 60% used in the foregoing examples is deemed the best upon all considerations. It is approximately the highest which can be attained in distilling --off a constant-boiling mixture of isopropanol and water, and thus permits the lowest temperature and pressure which can be used without incurring the expense of further reconcentration of the acid while the operating temperature of 100 de' grees C. can be conveniently held constant.

In the foregoing examples the process was carried out in the absence of any solvent for propylene other than the isopropanol produced in the operation. Where isopropanol is included in the contents of the autoclave at the outset of the operation, either as a residue from a previous operation or as a reagent otherwise provided, the operation is not substantially changed in character, although the final equilibrium and the time, the pressure and the degree of agitation for eflicient operation will necessarily be somewhat altered,

the general .tendency of such inclusion being to increase the relative amount of ether in the prodvucts.

The aqueous layer, weighing only g. was not analyzed, owing to its small content apart from the acid. The other layer, upon distillation, yielded 30 g. of isopropanol, 15.5 g. of diisopropy ether and about 64 g. of chloroform.

In the foregoing example the pressures were substantially below the optimum for the acid concentration and temperature used, but an economicallyfeasible rate of reaction was maintained by reason of the use of the auxiliary solvent.

In every application of my process the maintenance of extended surfaces of contact between the propylene and the dilute acid is essential for a commercially practical rate of operation, and agitation sufficient to maintain the contents of the apparatus in a foamy or finely divided and intimately min'gled condition is therefore an es- In laboratory operation in a small autoclave such agitation may conveniently be produced by a magnetically operated stirrer vibrating vertically, while in commercial operation any known or suitable means for the purpose may be used.

It will be understood that in place ofthe sul- The upper concentration.

I claim:

1. The procesafor hydrating propylene, which consists inmaintaining intimate contact of propylene with sulfuric acid of approximately 60% concentration by weight, at a temperature of approximately 100 degrees C. and under a pressure of not less than 300 lbs. gage, the molal ratio of propylene to water being not over 5 to 1.

2. The improvement, in the Process of hydrating propylene by heatingthe same in the presence of dilute sulphuric acid and under elevated pressure, which resides in the addition, to the reaction mixture, of a solvent for propylene other than a product of the reactio which is liquid under the conditions of temperature and pressure'at which the reaction is conducted.

3. The improvement, in the process of hydrating propylene by heating the same in the presence ofdilute sulphuric acid and under elevated pressure, which resides in the addition, to the reaction mixture, of chloroform as a solvent for the propylene.

4. In a process for hydrating propylene, the

about 180 C., inversely with the acid concentration, said inverse variation being such that at the different specific acid concentrations of about 20%, about 30%, about 40%, about and about the corresponding temperatures are respectively between about 150 C. and about 180 0.; about 140 C. and about 170 0.; about 130 C. and about 160 0.; about 120 C. and about 150 C.; and about 100 C. and about 130 C. and such that at acid concentrations intermediate between the aforesaid different specific concentrations, the corresponding temperature ranges are substantially those temperature ranges which are obtained by interpolation from the aforesaid different specific acid concentrations and the aforesaid specific corresponding temperature ranges, the propylene being under a pressure of at least% of that necessaryto maintainadensity of about 0.23 in the propylene at the reaction temperature.

5. In a process for hydrating propylene, the step which comprises maintaining intimate contact of propylene with a dilute solution of a nonvolatile inorganic acid of a concentration, by weight, between about 20% and about 65%, at a temperature variable, between about C. and

about 180 C., inversely with the acid concentration, said inverse variation being such that at the different specific acid concentrations of about 20%, about 30%, about 40%, about 50%, and about 60%, the corresponding temperatures are respectively between about 150 C. and about 180 0.; about 140 C. and about 170 0.; about 130 C. and about 160 0.; about C. and about 150 C.; and about 100 C. and about C. and such that at acid concentrations intermediate between the aforesaid different specific concentrations, the corresponding temperature ranges are substantially those temperature ranges which are obtained by interpolation from the aforesaid different specific acid concentrations and the aforesaid corresponding temperature ranges, the

propylene being under a pressure of at least 80% of that necessary to maintain a density oi about 0.23 in the propylene at the reaction temperature, the molal ratio of propylene to water being-not over about 5 to 1.

6. In a process for hydrating propylene, the step which comprises maintaining intimate contact of propylene with a dilute sulphuric acid of a concentration, by weight, between about 20% and about 65%, at a temperature variable, between about 100 C. and about 180 C. inversely with the acid concentration, said inverse variation being such that at the difierent specific acid concentrations of about 20%, about 30%, about 40%, about and about the corresponding temperatures are respectively between about 150 C. and about 180 C.; about 140 C. and about 170 C.; about 130 C. and about 160 0.; about 120 C. and about 150 C.; and about 100 C. and about 130 C. and such that at acid concentrations intermediate between the aforesaid difierent specific concentrations, the corresponding temperature ranges are substantially those 1 temperature ranges which are obtained by interpolation from the aforesaid different specific acid concentrations and the aforesaid corresponding temperature ranges, the propylene being under a pressure offat least 80% of that necessary to maintain a density of about 0.23 in the propylene at the reaction temperature.

7. In a process for hydrating propylene, the step which comprises maintaining intimate contact of propylene with dilute sulphuric acid of a concentration, by weight, between about 20% and about at a temperature variable, between about 100 C. and about 180 C., inversely with the acid concentration, said inverse variation being.such that at the different specific acid concentrations of about 20%, about 30 about 40%,

about 50% and about 60%,the corresponding temperatures are respectively betweenabout 150 C. and about 180 C.; about 140 C. and about 170 C.; about 130 C. and about 180 C.; about a pressure of at least of that necessary to.

maintain a density of about 0.23 in the propylene at the reaction temperature, the molal ratio of propylene to water being not over about 5 to 1.

8. In a process for hydrating propylene to produce a major quantity of isopropanol and a minor quantity of di-isopropyl ether, the step which comprises'maintaining intimate contact of propylene with dilute sulphuric acid of a-concentration, by weight, between about 20%. and about 65%, at a temperature variable between about C. and about 180 C., inversely with the acid concentration, said inverse variation being such that at the diflerent specific acid concentrations of about 20%, about 30%, about 40%, about 50% and about 60%, the corresponding temperatures are respectively between about 150' C. and

about 180 C.; about 140 C. and about 170 C.;

about 130 C. and'about 160 C.; about C. and about 150 C.; and about 100 C. and about C. and such that at acid concentrations intermediate between the aforesaid difieredit specifduce a major quantity of di-isopropyl ether and a minor quantity of' isopropanol, the step which comprisesmaintaining intimate contact of propylene with dilute sulphuric acid of a concentration, by weight, between about 20% and about 6 at a temperature variable, between about 100 C. and about 180 C., inversely with the acid concentration, said inverse variation being such that at the different specific acid concentrations of about 20%, about 30%, about 40%, about 50% and about 60%, the corresponding temperatures are respectively between about 150 C. and about180" C.; about C. and about 170 C.;

.about 130 C. and about 160 C.; about 120 C.

and about C.; and about 100 C. and about 130 C. and such that at acid concentrations intermediate between the aforesaid difl'erent' specific concentrations, the corresponding temperature ranges are subs ntially those temperature rangeswhich are ob ained by interpolation from the aforesaid diflererit specific acidconcentrations and the aforesaid corresponding temperature ranges, the propylene being under a pressure of at least 80% of that necessary to maintain a density of about 0.23 in the propylene at the reaction temperature, the molal ratio of propylene to water {being between about 2 to 1 and about 5 to 1. i a

10. In a process for hydrating propylene, the step which comprises maintaining intimate contact of propylene with a dilute solution of a nonvolatile inorganic acid of a concentration, by weight, between about 20% and'about 65%, at a temperature variable, between about 100 C. and

, about 180 C., inversely with the acid concentration, said inverse variation being such that at the diiferent specific acid concentrations of about 20%, about 30%, about 40%,about 50% and about 60%, the corresponding temperatures are respectively between about 150 C. and about 180 C.;

about 140 C. and about 170 C.; about 130 C. and about C.; about 120 C. and about 150 C.; andabout 100 C. and about 130 C. and such that at acid concentrations intermediate between the aforesaid different specific concentrations,

the-corresponding temperature ranges are sub-' stantially those temperature ranges which are obtained by interpolation from the aforesaid different specific acid concentrations and the aforesaid specific corresponding temperature ranges, the propylene being under a pressure of at least 80% of that necessary to maintain a density of about 0.23 in the propylene at the reaction temperature and maintaining said intimate. contact of propylene with the dilute solution or a nonvolatile. inorganic acid until about 90% of the equilibrium quantity of the endproducts of the said process for hydrating propylene is formed and then separating .the said products from the reaction 

